The present invention relates to control of a radio communications system base station, and more particularly to a control method which reduces power consumption and traffic handling capacity in a radio communications system base station without harshly affecting ongoing calls within the cell served by the base station.
In a radio communications system having at least one base station (BS), such as in a cellular telephone system, the base station provides service to mobile units located within a predefined geographical area. Such base stations are expected to operate during power failures that generally affect the location of the base station. Consequently, there is a need to provide an alternative ("backup") source of power to a base station which will be utilized when the usual source of base station power has failed. Suitable backup sources of power may be batteries or in some circumstances, diesel-powered electric generators.
A base station site having, for example, 72 transceivers (typically, a base station site has between 10 and 100 transceivers), each transmitting 50 Watts (W) of power with a power efficiency of 25% requires (50/0.25)*72=14400 W of power to operate. Normally, a 24 volt system is used for radio base stations, so an exemplary electric current requirement for a base station during times of heavy loads would be 14400/24=600 amp. Providing this amount of power during a failure of the main power supply requires a backup power supply to consist of many costly batteries or diesel-powered electric generators. Furthermore, accommodating the physical bulk of these backup power supplies may require that the base station plant floor be reinforced, and that the size of the base station plant be increased. Consequently, battery and plant costs commonly constitute the major investments for base station operators, and can even make it impossible to build some base station sites.
Thus, there is a need to provide a way for a base station to continue to operate during a power outage while at the same time reducing the cost and size of the backup power supply.
There are also circumstances other than failure of the main power supply, during which it would be advantageous to reduce the power consumption of the base station. For example, the overheating of equipment, or the occurrence of a fire could warrant reducing the base station power consumption. Similarly, there are circumstances when it is desirable to reduce the traffic handling capacity of the base station. During such transitions to reduced power consumption and/or reduced traffic handling capacity, it is still desirable to minimally affect ongoing communications traffic within the cell served by the base station. Thus, there is a need for a way to gradually reduce the power consumption and/or the traffic handling capacity of the base station in a way that reduces the disturbance to communications traffic capacity in the cell.